Electric Vehicles Sell Power Back to the Grid

Delaware Test Fleet Makes Money by Serving as an
Electricity Reserve

In the 1990s, Willett Kempton, a professor at the
University of Delaware, proposed in a paper that electric vehicles could
help pay for themselves by selling power back to the grid. When no one
jumped on the idea, he decided to develop the technology himself.

Now, the pilot project he spearheaded at the university in conjunction
with power-plant operator NRG Energy Inc. brings in
roughly $110 a month per electric vehicle. The
operation uses software to link a minimum of nine electric vehicles, mostly
Mini Coopers, together into a virtual power
plant on wheels that can both draw energy from the grid and discharge energy
when needed.

"We're not earning enough money to get rich," says Dr.
Kempton. But "it earns money, and it earns more money than it costs to do
it."

The vehicles—which come with chargers that allow for a
two-way flow of energy and have a custom-made circuit board added to control
the connection with the other cars and grid—essentially are being used as a
short-term ministorage facility by PJM Interconnection,
the operator of the electricity-transmission system in much of the Eastern
U.S.

When more electricity is produced than is required,
PJM can discharge power to the car batteries for storage; when demand
rises, it can draw the juice back out. The utility agrees to pay for the
reserved capacity whether it uses it or not, and the controller in the
vehicle ensures that the battery isn't drained to the point that the car
can't be driven.

Scott Baker, a senior business-solutions analyst at
PJM, says the grid operator sees electric
vehicles as potential stabilizers for the system, helping to keep
frequencies smooth, especially as intermittent alternative-energy sources
like solar are added to the grid.

The Delaware project requires that a certain number of
vehicles be strung together because PJM's
system won't recognize a "power plant" with less than 100 kilowatts of
capacity, which is about what nine vehicles can provide, Dr. Kempton says.
But heenvisions a day when there could be
hundreds of thousands of electric cars selling power to the grid while
plugged in at home or the office, making the vehicles more affordable
for owners.

University of Delaware electric cars act as a reserve for the power grid,
discharging electricity when needed. Evan Krape/University of Delaware

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That day, however, could be a
long way off. One issue is that many EVs don't come with two-way chargers,
which Dr. Kempton estimates would cost around $200 per car if auto makers
were to design them into new EVs. Another issue is that the control boards
are not commercially available, though Dr. Kempton says there have been
promising discussions with two big auto makers and an auto-parts
manufacturer.

And laws and regulations have to change before cars can be
used as power sources. Although the Federal Energy
Regulatory Commission has passed rules that allow for alternative
storage technologies, other regulatory bodies have been slower to do the
same.

Dr. Kempton worked with Delaware's
utility commission to create the needed regulations, and the state
legislature passed a law allowing vehicles to sell power back to the grid.

Still, the success of the Delaware project has inspired
other research, says Scott Fisher, the director of alternative-energy
services at NRG, which has licensed the
vehicle-to-grid technology used in Delaware. NRG
says it now plans to test whether electric vehicles could power a building
and will apply for funds from a $6 million pool of EV-to-grid research money
available from California's Energy Commission.

"I'm not saying it's a 100% slam dunk," Mr. Fisher says.
"But it's important enough to warrant the time and energy and expense."

The U.S. military, meanwhile,
has a $30 million project in the works to test
vehicle-to-grid technology on five bases, including Los Angeles Air Force
Base, starting this fall.